[PATCH 0/2] Fixes for TCG/HVF warning of CPUID_HT and CPUID_EXT3_CMP_LEG

[PATCH 0/2] Fixes for TCG/HVF warning of CPUID_HT and CPUID_EXT3_CMP_LEG

[Xiaoyao Li]

Starting from QEMU v10.0.0, QEMU hits warnings when vcpus >= 2 with TCG

 qemu-system-x86_64: warning: TCG doesn't support requested feature: CPUID.01H:EDX.ht [bit 28]
 qemu-system-x86_64: warning: TCG doesn't support requested feature: CPUID.80000001H:ECX.cmp-legacy [bit 1]

For HVF, it should have the same warning of CPUID.01H:EDX.ht [bit 28].

This series tries to fix them.

Xiaoyao Li (2):
  i386/tcg: Make CPUID_HT and CPUID_EXT3_CMP_LEG supported
  i386/hvf: Make CPUID_HT supported

 target/i386/cpu.c           | 8 +++++---
 target/i386/hvf/x86_cpuid.c | 2 +-
 2 files changed, 6 insertions(+), 4 deletions(-)

-- 
2.43.0

[PATCH 1/2] i386/tcg: Make CPUID_HT and CPUID_EXT3_CMP_LEG supported

[Xiaoyao Li]

Since commit c6bd2dd63420 ("i386/cpu: Set up CPUID_HT in
x86_cpu_expand_features() instead of cpu_x86_cpuid()") and
commit 99a637a86f55 ("i386/cpu: Set and track CPUID_EXT3_CMP_LEG in
env->features[FEAT_8000_0001_ECX]"), it gets warnings when booting the
VM with vcpus >= 2 and with tcg:

  qemu-system-x86_64: warning: TCG doesn't support requested feature: CPUID.01H:EDX.ht [bit 28]
  qemu-system-x86_64: warning: TCG doesn't support requested feature: CPUID.80000001H:ECX.cmp-legacy [bit 1]

This is because, after the two commits, CPUID_HT and CPUID_EXT3_CMP_LEG
are set in env->features[] when vcpus >=2 (in x86_cpu_expand_features())
later in x86_cpu_filter_features() it will check against the TCG supported
bits. However, current TCG doesn't mark the two bits as supported, hence
the warnings.

Fix it by adding the two bits to the supported bits of TCG since multiple
vcpus are supported by TCG.

Fixes: c6bd2dd63420 ("i386/cpu: Set up CPUID_HT in x86_cpu_expand_features() instead of cpu_x86_cpuid()")
Fixes: 99a637a86f55 ("i386/cpu: Set and track CPUID_EXT3_CMP_LEG in env->features[FEAT_8000_0001_ECX]")
Reported-by: Ewan Hai <ewanhai-oc@zhaoxin.com>
Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
---
 target/i386/cpu.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 1ca6307c72ef..c5a1fe1e8afe 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -776,11 +776,12 @@ void x86_cpu_vendor_words2str(char *dst, uint32_t vendor1,
           CPUID_PAE | CPUID_MCE | CPUID_CX8 | CPUID_APIC | CPUID_SEP | \
           CPUID_MTRR | CPUID_PGE | CPUID_MCA | CPUID_CMOV | CPUID_PAT | \
           CPUID_PSE36 | CPUID_CLFLUSH | CPUID_ACPI | CPUID_MMX | \
-          CPUID_FXSR | CPUID_SSE | CPUID_SSE2 | CPUID_SS | CPUID_DE)
+          CPUID_FXSR | CPUID_SSE | CPUID_SSE2 | CPUID_SS | CPUID_DE | \
+          CPUID_HT)
           /* partly implemented:
           CPUID_MTRR, CPUID_MCA, CPUID_CLFLUSH (needed for Win64) */
           /* missing:
-          CPUID_VME, CPUID_DTS, CPUID_SS, CPUID_HT, CPUID_TM, CPUID_PBE */
+          CPUID_VME, CPUID_DTS, CPUID_SS, CPUID_TM, CPUID_PBE */
 
 /*
  * Kernel-only features that can be shown to usermode programs even if
@@ -848,7 +849,8 @@ void x86_cpu_vendor_words2str(char *dst, uint32_t vendor1,
 
 #define TCG_EXT3_FEATURES (CPUID_EXT3_LAHF_LM | CPUID_EXT3_SVM | \
           CPUID_EXT3_CR8LEG | CPUID_EXT3_ABM | CPUID_EXT3_SSE4A | \
-          CPUID_EXT3_3DNOWPREFETCH | CPUID_EXT3_KERNEL_FEATURES)
+          CPUID_EXT3_3DNOWPREFETCH | CPUID_EXT3_KERNEL_FEATURES | \
+          CPUID_EXT3_CMP_LEG)
 
 #define TCG_EXT4_FEATURES 0
 
-- 
2.43.0

[PATCH 2/2] i386/hvf: Make CPUID_HT supported

[Xiaoyao Li]

Since Commit c6bd2dd63420 ("i386/cpu: Set up CPUID_HT in
x86_cpu_expand_features() instead of cpu_x86_cpuid()"), CPUID_HT will be
set in env->features[] in x86_cpu_expand_features() when vcpus >= 2.

Later in x86_cpu_filter_features() it will check against the HVF
supported bits. It will trigger the warning like

    qemu-system-x86_64: warning: host doesn't support requested feature: CPUID.01H:EDX.ht [bit 28]

Add CPUID_HT to HVF supported CPUID bits to fix it.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
---
Note, the issue is totally by my analysis (which should be the same as
the TCG warnings) because I don't have HVF environment to verify it.

If would be helpful if anyone can help reproduce it and test the patch
in HVF environment.
---
 target/i386/hvf/x86_cpuid.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/target/i386/hvf/x86_cpuid.c b/target/i386/hvf/x86_cpuid.c
index fa131b18c6d1..0798a0cbafb9 100644
--- a/target/i386/hvf/x86_cpuid.c
+++ b/target/i386/hvf/x86_cpuid.c
@@ -73,7 +73,7 @@ uint32_t hvf_get_supported_cpuid(uint32_t func, uint32_t idx,
              CPUID_MSR | CPUID_PAE | CPUID_MCE | CPUID_CX8 | CPUID_APIC |
              CPUID_SEP | CPUID_MTRR | CPUID_PGE | CPUID_MCA | CPUID_CMOV |
              CPUID_PAT | CPUID_PSE36 | CPUID_CLFLUSH | CPUID_MMX |
-             CPUID_FXSR | CPUID_SSE | CPUID_SSE2 | CPUID_SS;
+             CPUID_FXSR | CPUID_SSE | CPUID_SSE2 | CPUID_SS | CPUID_HT;
         ecx &= CPUID_EXT_SSE3 | CPUID_EXT_PCLMULQDQ | CPUID_EXT_SSSE3 |
              CPUID_EXT_FMA | CPUID_EXT_CX16 | CPUID_EXT_PCID |
              CPUID_EXT_SSE41 | CPUID_EXT_SSE42 | CPUID_EXT_MOVBE |
-- 
2.43.0

Re: [PATCH 1/2] i386/tcg: Make CPUID_HT and CPUID_EXT3_CMP_LEG supported

[Zhao Liu]

On Tue, May 13, 2025 at 11:16:51PM -0400, Xiaoyao Li wrote:
> Date: Tue, 13 May 2025 23:16:51 -0400
> From: Xiaoyao Li <xiaoyao.li@intel.com>
> Subject: [PATCH 1/2] i386/tcg: Make CPUID_HT and CPUID_EXT3_CMP_LEG
>  supported
> X-Mailer: git-send-email 2.43.0
> 
> Since commit c6bd2dd63420 ("i386/cpu: Set up CPUID_HT in
> x86_cpu_expand_features() instead of cpu_x86_cpuid()") and
> commit 99a637a86f55 ("i386/cpu: Set and track CPUID_EXT3_CMP_LEG in
> env->features[FEAT_8000_0001_ECX]"), it gets warnings when booting the
> VM with vcpus >= 2 and with tcg:
> 
>   qemu-system-x86_64: warning: TCG doesn't support requested feature: CPUID.01H:EDX.ht [bit 28]
>   qemu-system-x86_64: warning: TCG doesn't support requested feature: CPUID.80000001H:ECX.cmp-legacy [bit 1]
> 
> This is because, after the two commits, CPUID_HT and CPUID_EXT3_CMP_LEG
> are set in env->features[] when vcpus >=2 (in x86_cpu_expand_features())
> later in x86_cpu_filter_features() it will check against the TCG supported
> bits. However, current TCG doesn't mark the two bits as supported, hence
> the warnings.
> 
> Fix it by adding the two bits to the supported bits of TCG since multiple
> vcpus are supported by TCG.
> 
> Fixes: c6bd2dd63420 ("i386/cpu: Set up CPUID_HT in x86_cpu_expand_features() instead of cpu_x86_cpuid()")
> Fixes: 99a637a86f55 ("i386/cpu: Set and track CPUID_EXT3_CMP_LEG in env->features[FEAT_8000_0001_ECX]")
> Reported-by: Ewan Hai <ewanhai-oc@zhaoxin.com>

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2894

Then QEMU gitlab can track this fix.

> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> ---
>  target/i386/cpu.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)

Both HT and CMPLegacy depend on CPU topology (mutiple threads per
package), therefore, there's no need for extra work in TCG.

So,

Reviewed-by: Zhao Liu <zhao1.liu@intel.com>

Re: [PATCH 2/2] i386/hvf: Make CPUID_HT supported

[Zhao Liu]

On Tue, May 13, 2025 at 11:16:52PM -0400, Xiaoyao Li wrote:
> Date: Tue, 13 May 2025 23:16:52 -0400
> From: Xiaoyao Li <xiaoyao.li@intel.com>
> Subject: [PATCH 2/2] i386/hvf: Make CPUID_HT supported
> X-Mailer: git-send-email 2.43.0
> 
> Since Commit c6bd2dd63420 ("i386/cpu: Set up CPUID_HT in
> x86_cpu_expand_features() instead of cpu_x86_cpuid()"), CPUID_HT will be
> set in env->features[] in x86_cpu_expand_features() when vcpus >= 2.
> 
> Later in x86_cpu_filter_features() it will check against the HVF
> supported bits. It will trigger the warning like
> 
>     qemu-system-x86_64: warning: host doesn't support requested feature: CPUID.01H:EDX.ht [bit 28]
> 
> Add CPUID_HT to HVF supported CPUID bits to fix it.
> 
> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> ---
> Note, the issue is totally by my analysis (which should be the same as
> the TCG warnings) because I don't have HVF environment to verify it.
> 
> If would be helpful if anyone can help reproduce it and test the patch
> in HVF environment.

Ah, I found someone has reported a bug on HVF. In his log, there's the
ht warning:

https://gitlab.com/qemu-project/qemu/-/issues/2938

But I don't know if this fix can help on his bug...let's wait for his
feedback.

> ---
>  target/i386/hvf/x86_cpuid.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Anyway, this fix is fine for me, so,

Reviewed-by: Zhao Liu <zhao1.liu@intel.com>

Re: [PATCH 2/2] i386/hvf: Make CPUID_HT supported

[Zhao Liu]

On Thu, May 15, 2025 at 04:17:28PM +0800, Zhao Liu wrote:
> Date: Thu, 15 May 2025 16:17:28 +0800
> From: Zhao Liu <zhao1.liu@intel.com>
> Subject: Re: [PATCH 2/2] i386/hvf: Make CPUID_HT supported
> 
> On Tue, May 13, 2025 at 11:16:52PM -0400, Xiaoyao Li wrote:
> > Date: Tue, 13 May 2025 23:16:52 -0400
> > From: Xiaoyao Li <xiaoyao.li@intel.com>
> > Subject: [PATCH 2/2] i386/hvf: Make CPUID_HT supported
> > X-Mailer: git-send-email 2.43.0
> > 
> > Since Commit c6bd2dd63420 ("i386/cpu: Set up CPUID_HT in
> > x86_cpu_expand_features() instead of cpu_x86_cpuid()"), CPUID_HT will be
> > set in env->features[] in x86_cpu_expand_features() when vcpus >= 2.
> > 
> > Later in x86_cpu_filter_features() it will check against the HVF
> > supported bits. It will trigger the warning like
> > 
> >     qemu-system-x86_64: warning: host doesn't support requested feature: CPUID.01H:EDX.ht [bit 28]
> > 
> > Add CPUID_HT to HVF supported CPUID bits to fix it.
> > 
> > Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> > ---
> > Note, the issue is totally by my analysis (which should be the same as
> > the TCG warnings) because I don't have HVF environment to verify it.
> > 
> > If would be helpful if anyone can help reproduce it and test the patch
> > in HVF environment.
> 
> Ah, I found someone has reported a bug on HVF. In his log, there's the
> ht warning:
> 
> https://gitlab.com/qemu-project/qemu/-/issues/2938
> 
> But I don't know if this fix can help on his bug...let's wait for his
> feedback.

Amitai has confirmed this fix can resolve #2938. So I think it's
necessary to add the tag:

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2938

and CC this series to qemu-stable@nongnu.org.

Thanks,
Zhao

> > ---
> >  target/i386/hvf/x86_cpuid.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Anyway, this fix is fine for me, so,
> 
> Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
> 
> 

Re: [PATCH 0/2] Fixes for TCG/HVF warning of CPUID_HT and CPUID_EXT3_CMP_LEG

[Michael Tokarev]

On 14.05.2025 06:16, Xiaoyao Li wrote:
> Starting from QEMU v10.0.0, QEMU hits warnings when vcpus >= 2 with TCG
> 
>   qemu-system-x86_64: warning: TCG doesn't support requested feature: CPUID.01H:EDX.ht [bit 28]
>   qemu-system-x86_64: warning: TCG doesn't support requested feature: CPUID.80000001H:ECX.cmp-legacy [bit 1]
> 
> For HVF, it should have the same warning of CPUID.01H:EDX.ht [bit 28].
> 
> This series tries to fix them.
> 
> Xiaoyao Li (2):
>    i386/tcg: Make CPUID_HT and CPUID_EXT3_CMP_LEG supported
>    i386/hvf: Make CPUID_HT supported

This seems to be a qemu-stable material (10.0).
Applied to staging-10.0, please let me know if I shouldn't.

Thanks,

/mjt